BURIED IMPACT STRUCTURES FOUND IN MARSCRUST3 CRUSTAL THICKNESS MODEL: IDENTIFICATION, CLASSIFICATION, & SIGNIFICANCE

Identifying buried impact structures on Mars will aid in reconstructing the evolution of the surface and understanding the events responsible for the dichotomy observed. Edgar and Frey (2008) produced a global map of Quasi-Circular Depressions (QCDs) and Circular Thin Areas (CTAs) across Mars, using MOLA topography and the crustal thickness model (Cthick) by Neumann et al. (2004). Improved solutions from MRO gravity data allowed for the production of a new model (MarsCrust3), which provides a 20% increase in spatial resolution (Neumann et al., 2008). The new model calls for the re-evaluation of all previously mapped CTAs and identification of additional CTAs.

Each identified CTA is examined in MarsCrust3 and then assigned a confidence interval based upon geometry and strength of signature. QCDs found in MOLA topography are also identified and assigned a confidence interval. These two data sets are then cross-referenced to determine overlap. If the topography reveals that a feature is not an impact structure, the CTA is discarded from the final data set. However, the absence of a QCD does not negate the validity of the CTA.

Edgar and Frey (2008) found that the combined number of QCDs and CTAs suggested the highlands and lowlands are closer in age then previously thought. Preliminary work with MarsCrust3 shows the same relationship between these two regions. This improved spatial resolution will aid in determining more subtle, regional age relationships that could not be resolved in the old model. Cthick allows for the identification of features down to 300km in diameter, however MarsCrust3 allows for the identification of features down to 200km in diameter. Once the global data set of all QCDs and CTAs is complete, it will be possible to create a more accurate timeline of impact and resurfacing events across Mars.